JPS60222741A - Gas leak detector of low temperature double-shell tank - Google Patents

Abstract

PURPOSE:To detect the gas leak from an inner tank at an early stage and to detect the leaking point, by partitioning at least one part of the outer surface of the inner tank, and providing a gas-leak-detecting sampling means for every cell covered by a film. CONSTITUTION:Cells are formed in the roof part and the side plate part of an inner tank 1. A film 2 is provided in each cell so as to cover the cell wall. The outside of the film is contacted with the outer surface of the inner tank 1. A gas-leak-detecting sampling device 3 is provided between the outer surface of the inner tank and the film 2 in each cell. The part between the film 2 and an outer tank 4 is filled with pearlite 5. Nitrogen gas between the outer surface of the inner tank and the film 2 in each cell is sucked to a gas-leak detecting instrumentation by a pump, which is connected to the gas sampling device 3. Nitrogen gas is introduced into the space from a nitrogen feeding pipe and made to of flow through the space. When stored low-temperature liquid gas leaks from the inner tank, the gas is mixed into the flowing nitrogen gas. The gas is sampled and detected by the gas-leak detecting instrumentation.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a gas leak detection device for a double shell cryogenic tank.

Conventional technology Double-shell flat-bottom cryogenic tanks are widely used as large-scale storage tanks for low-temperature liquefied gases such as LPG and LNG, but large tanks of this type have a storage capacity of tens of thousands of tons. Since they contain a large amount of energy, the disaster would be enormous if they were destroyed, so safety management is extremely important. Therefore, it is important to detect cracks in the tank shell as early as possible before the tank is destroyed.

In a double-shell cryogenic tank, the inner tank serves as a storage tank for low-temperature liquefied gas, and the space between the inner tank and outer tank is filled with cold insulation material and seal gas to form a cold insulation layer. In order to detect cracks that have occurred in the tank shell, an inert gas such as nitrogen gas, which is generally used as a sealing gas for the cold insulation layer, is allowed to flow into the cold insulation layer from the outside, while at the same time it is placed at appropriate locations in the cold insulation layer. The method used was to sample the sealed gas from the sampling section and detect the stored gas components therein.

Now, perlite is often used as the cold insulation material for the sides and roof cold insulation layer of double-shell flat bottom cryogenic tanks, but this cold insulation material has poor breathability and leaks from cracks that occur in the inner tank shell. There was a drawback that it took a long time for the gas to pass through the cold layer and reach the sampling section. Furthermore, in large low-temperature tanks, the outer surface area of the inner tank is large, and even if a leak is detected, it takes time to locate the leak.

Purpose The present invention addresses the above-mentioned problems of the conventional gas leakage detection device for the conventional double-shelled flat-bottom cryogenic tank, and is capable of relatively quickly detecting gas leakage from the inner tank. It is an object of the present invention to provide a gas leakage detection device for a double-shelled low-temperature tank that can easily locate the approximate location of a leakage point.

Structure: The gas leakage button device of the present invention which achieves this object divides at least a part of the outer surface of the inner tank, and covers each compartment with a membrane that is bonded to the outer surface of the inner tank. In each compartment, a sampling means for detecting gas leakage is installed in the space between the outer surface of the inner tank and the above-mentioned membrane. It is characterized by having been established.

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

The left half of Fig. 1 is an example in which the entire roof and side panels of the inner tank l are partitioned, and as shown in Fig. 2 the top surface, multiple parts A
, B, C, . . . , a membrane 2 whose periphery is adhered to the outer surface of the inner tank 1 is stretched.

As shown in FIG. 3, a gas sampling device 3 for detecting gas leakage is provided between the outer surface of the inner tank and the membrane 2 in each compartment. Perlite 5 is filled between the membrane 2 and the outer tank 4.

A nitrogen gas supply pipe (not shown) is connected to the space between the outer surface of the inner tank 1 and the membrane 2 in each compartment, so that nitrogen gas is supplied to the space. On the other hand, gas leak detection instrumentation is connected to the gas sampling device 3 via a pump (not shown). Therefore, if the nitrogen gas between the outer surface of the inner tank of each compartment and the membrane 2 is sucked into the gas leak detection instrumentation using this pump, the nitrogen gas will be introduced into the space from the nitrogen gas supply pipe and fill the space. If the stored low-temperature liquefied gas leaks from the inner tank, it will be mixed into the flowing nitrogen gas and sampled, and detected by the gas leak detection instrumentation.

Therefore, in the event of a gas leak, it will be detected more quickly than in the past, and the location of the leak can be determined to be within the area where the gas leak was detected, so countermeasures can be taken early. can.

The right half of FIG. 1 shows an example in which only the outer surface of the roof of the inner tank 1 is partitioned and covered with the membrane 2. Even when perlite is used as a cold insulation material, the sides of the double-shell low-temperature tank are kept cool by using elastic materials such as glass wool in contact with the outer surface of the inner tank to prevent perlite from settling due to temperature changes caused by repeated use of the tank and empty tank. A layer of cold insulation material is provided to prevent sealing gas and leakage gas. Yo□yo 2. □Move in the direction of 5 degrees. However, the roof is not provided with a layer of glass wool for cold insulation, and since the roof is nearly horizontal, leaking gas does not move easily due to differences in specific gravity.

Therefore, no compartments covered with the membrane 2 are provided on the side parts where gas moves relatively easily, and compartments are provided only in the roof cold insulation part where leakage gas is difficult to move.

In order to facilitate the flow of nitrogen gas through the space between the outer surface of the inner tank and the membrane 2 in each compartment, it is desirable to provide a spacer to ensure a ventilation space between the outer surface of the inner tank and the membrane 2. It is convenient to use a breathable cold insulating material such as glass wool as the spacer because it forms a cold insulating layer that also serves as a gas passage. In addition to this, shaped steel, wood, plastic, etc. with various cross sections may be appropriately arranged.

In addition, since leakage of gas from the inner tank shell plate is practically limited to the weld line, it is preferable to arrange the spacer so that the gas passage is formed above the weld line. When channel steel is used as a spacer, if the tips of both flanges are placed in contact with both sides of the weld line, a gas flow path will be formed inside the spacer.

Furthermore, since gas leakage occurs only at the weld line, sufficient effects can be obtained even if a section is provided where the membrane is stretched in a band shape over the weld line, rather than over the entire outer surface of the inner tank.

Polyester, polyethylene, etc. can be used as the membrane used in the present invention, and epoxy resin can be used as the adhesive for bonding the membrane to the outer surface of the inner tank.

Note that when pearlite is used as the cold insulating material, the film is pressed against the outer surface of the inner tank by its own weight, so there is no need to use an adhesive.

Effects As described above, according to the present invention, gas leakage from the inner tank can be detected at an early stage, and the location of the leakage can be easily determined, so countermeasures can be taken without delay. Significant effects on safety management can be obtained.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the present invention, the left half shows an example in which the roof and side panels are partitioned, the right half shows an example in which only the roof is partitioned, and Fig. 2 shows the inner tank. A top view of the roof section, and FIG. 3 is an enlarged sectional view of the roof section. l...Inner tank 2...Membrane 3...Gas sangrig means 4...Outer tank 5...Cold insulation material A, B, C,...Division

Claims (6)

[Claims] (1) Storage liquefaction from the inner tank shell of a double-shell low-temperature tank that has an inner tank and an outer tank, with the inner tank serving as a storage space for low-temperature liquefied gas, and the space between the inner and outer tanks serving as a cold insulation layer. In a gas leak detection device, at least a part of the outer surface of the inner tank is divided, a membrane covering each compartment and the outer surface of the inner tank is bonded to the outer surface of the inner tank is provided, and each compartment is separated from the outer surface of the inner tank. Gas leak detection characterized in that a gas leak detection sampling means is provided in the space between the membrane and a gas leak detection instrumentation is provided for detecting the gas leak in each section of the gas sampled by the sampling means. Device. (2) The device according to claim 1, further comprising a spacer that forms a ventilation space between the membrane and the outer surface of the inner tank. (3) The device according to claim 2, wherein the spacer is a breathable cold insulating material. (4) The device according to claim 2, wherein the spacer is a rigid shaped member. (5) The device according to claim 2, wherein the spacer is disposed at least on the weld line of the inner tank so as to form a ventilation space. (6) The device according to claim 1, wherein the section is provided in a band shape including the weld line of the inner tank.